Earth Science: Satellite Gap Ignites Concern Among Wildfire Responders
SAN FRANCISCO — As wildfires plague the drought-stricken southern United States, National Oceanic and Atmospheric Administration (NOAA) officials who monitor the blazes warn that a looming gap in space-based observations threatens their ability to alert firefighters, warn the public of health hazards and monitor global climate change.
Data from the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA’s Earth-observing satellites Terra and Aqua has been used for more than a decade to detect fires, identify their perimeters and track the billowing clouds of smoke they produce. The aging MODIS instruments are not likely to last much longer, however, and scientists are concerned that the instruments destined to replace them will not be launched quickly enough to provide continuous fire monitoring.
“These are vital dataset for savings lives and property,” said Mitch Goldberg, program scientist for NOAA’s Joint Polar Satellite System (JPSS). “They go into weather forecast models and hazard alert systems.”
The JPSS program was established in early 2010 when White House officials announced plans to scrap the National Polar-orbiting Operational Environmental Satellite System (NPOESS), a joint effort of NOAA and the Defense Department to create a single satellite capable of meeting civil and military weather monitoring goals. When NPOESS was halted, NOAA was given the task of developing the next polar-orbiting spacecraft for civil needs while the Air Force was charged with building the military weather satellites.
To implement the new strategy without delaying the launch of JPSS, NOAA needed an infusion of funding in 2011. That money was not appropriated because Congress failed to pass individual agency spending bills, opting instead to freeze most federal budgets at 2010 levels. The first JPSS spacecraft is now scheduled for launch in 2017, said NOAA spokesman John Leslie. Agency officials are likely to face a period of months or years between the time MODIS observations end and observations drawn from the next generation of polar-orbiting sensors begin, Goldberg said.
Until recently, government officials anticipated that a joint NASA-NOAA program, the NPOESS Preparatory Project (NPP) scheduled for launch Oct. 25, would bridge any gap in observations between the end of the Terra and Aqua programs and JPSS. A report issued June 2 by the NASA Inspector General, however, highlighted technical issues associated with the NPP sensor most valuable to fire detection, the Visible Infrared Imaging Radiometer Suite (VIIRS), and another NPP instrument the Crosstrack Infrared Sounder. That report suggested that instead of providing observations for seven years as previously planned, the sensors may only work for three years. If VIIRS does stop working after three years, there could be a lengthy gap without observations, NOAA officials said.
NOAA officials rely heavily on space-based observations drawn from many different satellites to detect fires and monitor their impact. In addition to Terra and Aqua, data is drawn from the Advanced Very High Resolution Radiometer (AVHRR) on NOAA’s Polar Orbiting Environmental Satellites, and NOAA’s Geostationary Operational Environmental Satellite imager.
The instruments in geostationary orbit provide critical updates on fires and smoke with observations made every 15 minutes while instruments flying on NOAA’s polar satellites and NASA’s Terra and Aqua offer more detailed information on the precise location of fires because of their higher spatial resolution, NOAA officials said. With the two complementary data sets, NOAA officials can detect fires, determine their intensity, track smoke clouds and feed observations into global climate models. The extensive amount of carbon and aerosol emissions released by fires is an extremely important component of global climate models, said Ivan Csiszar, environmental monitoring branch chief in NOAA’s Satellite Meteorology and Climatology Division.
NOAA scientists said their ability to pinpoint the location of smaller fires is expected to improve substantially when they gain access to VIIRS data. Not only will VIIRS offer more detailed imagery due to its smaller pixel size, but it will also obtain data of larger swaths of land with each orbit to guarantee that no gaps are observed between swaths, Goldberg said. In addition, VIIRS will provide images with consistently high resolution. Current space-based instruments including MODIS and AVHRR produce images with higher resolution near the center of each swath and degraded accuracy near the outside edges, Goldberg said.
In NOAA’s National Environmental Satellite Data and Information Service’s Center for Satellite Applications and Research, meteorologists look at imagery around the clock to confirm the presence of fires detected by the agency’s algorithms and identify any fires that those computer programs may have missed. Information on fires and the smoke produced is then made publicly available through NOAA websites, said Mark Ruminski, NOAA’s fire weather team leader. That information is used by NOAA’s National Weather Service, the U.S. Forest Service, the U.S. Environmental Protection Agency as well as state and local government agencies.
Firefighters around the nation use infrared imagery drawn from satellites to identify fire perimeters, track the spread of blazes and determine their intensity, said Ken Frederick, spokesman for the National Interagency Fire Center in Boise, Idaho. For extremely large fires, like the Wallow blaze in Arizona that began in late May and claimed more than 2 million square kilometers by mid-July, satellite-based imagery often can be obtained faster than aerial data and the quality is “probably just as good,” Frederick added.
In addition to monitoring the size and location of fires, NOAA officials use satellite data to map the spread of smoke which can present serious health problems. Once smoke from a fire is detected, NOAA officials gather data on the type of fuel burning, weather conditions, and the size and intensity of the blaze. That information is used in computer models that attempt to predict how far and how fast the smoke will travel across the country and around the world, Ruminski said.